Generally, various machine tools are used to machine the workpiece with a machining tool. For example, during boring operation, a boring tool equipped with a boring tool tip and installed in the rotary spindle of the machine tool which rotates the said boring tool at a high speed is fed along a preparatory hole so that a precise hole is drilled in the predetermined position along the machining diameter of the cutting edge.
In regular cases, the boring bar is made so-called stub boring future and used to boring a hole in workpieces such as connecting rods, so that it is relatively long and has a small diameter. This is to avoid interference with jigs for clamping the workpiece or interference with the shape of the boring hole itself. For this reason, the boring bar is subject to deflection caused by cutting resistance, resulting in chattering marks (including so-called regenerative chattering marks) on the workpiece.
The vibration suppression boring bar disclosed in patent document 1 is known to avoid this problem. The boring bar shown in patent document 1 features a dynamic damper and it has a blind hole in the center, in which a pipe magnet is inserted in a sliding state, which is filled with another rod-shaped magnet which repels to the said pipe magnet that is placed in the center of the pipe magnet at a certain gap.    Japanese Laid-open Patent Publication No.H03(1991)-86404